In technology of assembling ships, aircraft, and the like, attaching an external panel to an internal part requires an alignment of relative positions. For example, a main wing of an aircraft has a box structure including beams and ribs. A base end part of the main wing has a frame structure to be joined with a fuselage. The fuselage has a fixing part (bracket) substantially having a cylindrical structure to receive the base end part of the main wing. The base end part of the main wing is inserted into the fixing part and joined to the same to form a tea-caddy-like structure. The fixing part of the fuselage is constructed to have two plate members that hold therebetween a plate member constituting the base end part of the main wing. The surface of the plate member of the base end part faces the plate members of the fixing part with a gap of about several millimeters between them. Each of the plate members is made of conductive material such as aluminum alloy and carbon fiber. In the joining work of the fuselage and main wing, they are aligned and adjusted to each other to establish a predetermined positional relationship. Thereafter, a spacer adjusted to the shape of the gap is inserted into the gap and is joined to the adjoining members. The same is carried out when manufacturing a fuselage by separately preparing a front fuselage, a middle fuselage, and a rear fuselage and joining them together into one body. Related arts are, for example, Japanese Patent Publication NO. 4832512 and Japanese Unexamined Patent Application Publication No. 2015-79979.